1. Field of the Invention
The invention relates to a high-pressure pump.
2. Description of Related Art
A high-pressure pump used for supplying fuel to injectors of an internal combustion engine, such as a diesel engine or a gasoline engine, includes a plunger capable of reciprocating in a cylinder, and a housing having a pressurizing chamber in which the fuel is pressurized by the plunger, and a fuel chamber through which the fuel flows toward and from the pressurizing chamber. A known example of the high-pressure pump (as disclosed in, for example, Japanese Patent Application Publication No. 2010-185410 (JP-A-2010-185410)) includes a damper device for dampening pressure pulsation of the fuel which occurs due to reciprocating movement of the plunger.
The high-pressure pump as described in JP-A-2010-185410 includes a spring that biases the plunger in such a direction as to increase the volume of the pressurizing chamber, and a spring seat (corresponding to an oil seal holder 25 shown in JP-A-2010-185410) that is fixed to the housing and is in abutting contact with one end of the spring. Also, a space (corresponding to a passage 107 shown in JP-A-2010-185410) through which the fuel flows is provided between the bottom of the spring seat and the housing, and the space communicates with the fuel chamber via a fuel passage (corresponding to a passage 108 shown in JP-A-2010-185410) formed in the housing.
In operation, the spring seat may receive heat of engine oil for lubricating cams, springs, etc., to be heated to a high temperature, and the fuel flowing in the above-mentioned space may receive the heat from the spring seat, so that the temperature of the fuel in the high-pressure pump may be generally increased. Due to the temperature rise of the fuel, vapor may be produced in the high-pressure pump, and may affect control of the discharge amount of the high-pressure pump. In particular, when the engine is operating in fuel-cut mode, or when the engine is stopped while it is in a high-load operating condition (i.e., when the engine is in a condition of so-called “high-temperature dead soak”), for example, the fuel having a high temperature remains in the high-pressure pump, and the above-described situation may occur.